I have a basic question to ensure If I really have understood something.
Lets assume that person A wants to give person B 5 Bitcoins.
Do the miners have to walk through the entire Blockhain beginning from 2009 up to know to check my bank balance in order I have still 5 Bitcoins as balance ? If this is the case and maybe the half world would use bitcoins, there are endless blocks to be read to validate each transactions. ???

Let’s say A wants to send 5 bitcoins to B.Some work needs to be done in order to carry the 5 coins from A to B.This particular work is done by miners who solves a block so that the transaction can be relayed for a fee which u are paying through your wallet.Blockchain ensures that this particular work is shown in the network i.e. the addresses involved,fees paid, miner’s details etc.